/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2012 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.7.2
 *
 */
(function($, window) {

	$window = $(window);

	$.fn.lazyload = function(options) {
		var elements = this;
		var settings = {
			threshold : 0,
			failure_limit : 0,
			event : "scroll",
			effect : "show",
			container : window,
			data_attribute : "original",
			skip_invisible : true,
			appear : null,
			load : null
		};

		function update() {
			var counter = 0;

			elements.each(function() {
				var $this = $(this);
				if (settings.skip_invisible && !$this.is(":visible")) {
					return;
				}
				if ($.abovethetop(this, settings)
						|| $.leftofbegin(this, settings)) {
					/* Nothing. */
				} else if (!$.belowthefold(this, settings)
						&& !$.rightoffold(this, settings)) {
					$this.trigger("appear");
				} else {
					if (++counter > settings.failure_limit) {
						return false;
					}
				}
			});

		}

		if (options) {
			/* Maintain BC for a couple of versions. */
			if (undefined !== options.failurelimit) {
				options.failure_limit = options.failurelimit;
				delete options.failurelimit;
			}
			if (undefined !== options.effectspeed) {
				options.effect_speed = options.effectspeed;
				delete options.effectspeed;
			}

			$.extend(settings, options);
		}

		/* Cache container as jQuery as object. */
		$container = (settings.container === undefined || settings.container === window) ? $window
				: $(settings.container);

		/* Fire one scroll event per scroll. Not one scroll event per image. */
		if (0 === settings.event.indexOf("scroll")) {
			$container.bind(settings.event, function(event) {
				return update();
			});
		}

		this
				.each(function() {
					var self = this;
					var $self = $(self);

					self.loaded = false;

					/* When appear is triggered load original image. */
					$self
							.one(
									"appear",
									function() {
										if (!this.loaded) {
											if (settings.appear) {
												var elements_left = elements.length;
												settings.appear
														.call(self,
																elements_left,
																settings);
											}
											$("<img />")
													.bind(
															"load",
															function() {
																$self
																		.hide()
																		.attr(
																				"src",
																				$self
																						.data(settings.data_attribute))[settings.effect]
																		(settings.effect_speed);
																self.loaded = true;

																/*
																 * Remove image
																 * from array so
																 * it is not
																 * looped next
																 * time.
																 */
																var temp = $
																		.grep(
																				elements,
																				function(
																						element) {
																					return !element.loaded;
																				});
																elements = $(temp);

																if (settings.load) {
																	var elements_left = elements.length;
																	settings.load
																			.call(
																					self,
																					elements_left,
																					settings);
																}
															})
													.attr(
															"src",
															$self
																	.data(settings.data_attribute));
										}
									});

					/* When wanted event is triggered load original image */
					/* by triggering appear. */
					if (0 !== settings.event.indexOf("scroll")) {
						$self.bind(settings.event, function(event) {
							if (!self.loaded) {
								$self.trigger("appear");
							}
						});
					}
				});

		/* Check if something appears when window is resized. */
		$window.bind("resize", function(event) {
			update();
		});

		/* Force initial check if images should appear. */
		update();

		return this;
	};

	/* Convenience methods in jQuery namespace. */
	/* Use as $.belowthefold(element, {threshold : 100, container : window}) */

	$.belowthefold = function(element, settings) {
		var fold;

		if (settings.container === undefined || settings.container === window) {
			fold = $window.height() + $window.scrollTop();
		} else {
			fold = $container.offset().top + $container.height();
		}

		return fold <= $(element).offset().top - settings.threshold;
	};

	$.rightoffold = function(element, settings) {
		var fold;

		if (settings.container === undefined || settings.container === window) {
			fold = $window.width() + $window.scrollLeft();
		} else {
			fold = $container.offset().left + $container.width();
		}

		return fold <= $(element).offset().left - settings.threshold;
	};

	$.abovethetop = function(element, settings) {
		var fold;

		if (settings.container === undefined || settings.container === window) {
			fold = $window.scrollTop();
		} else {
			fold = $container.offset().top;
		}

		return fold >= $(element).offset().top + settings.threshold
				+ $(element).height();
	};

	$.leftofbegin = function(element, settings) {
		var fold;

		if (settings.container === undefined || settings.container === window) {
			fold = $window.scrollLeft();
		} else {
			fold = $container.offset().left;
		}

		return fold >= $(element).offset().left + settings.threshold
				+ $(element).width();
	};

	$.inviewport = function(element, settings) {
		return !$.rightofscreen(element, settings)
				&& !$.leftofscreen(element, settings)
				&& !$.belowthefold(element, settings)
				&& !$.abovethetop(element, settings);
	};

	/* Custom selectors for your convenience. */
	/* Use as $("img:below-the-fold").something() */

	$.extend($.expr[':'], {
		"below-the-fold" : function(a) {
			return $.belowthefold(a, {
				threshold : 0,
				container : window
			});
		},
		"above-the-top" : function(a) {
			return !$.belowthefold(a, {
				threshold : 0,
				container : window
			});
		},
		"right-of-screen" : function(a) {
			return $.rightoffold(a, {
				threshold : 0,
				container : window
			});
		},
		"left-of-screen" : function(a) {
			return !$.rightoffold(a, {
				threshold : 0,
				container : window
			});
		},
		"in-viewport" : function(a) {
			return !$.inviewport(a, {
				threshold : 0,
				container : window
			});
		},
		/* Maintain BC for couple of versions. */
		"above-the-fold" : function(a) {
			return !$.belowthefold(a, {
				threshold : 0,
				container : window
			});
		},
		"right-of-fold" : function(a) {
			return $.rightoffold(a, {
				threshold : 0,
				container : window
			});
		},
		"left-of-fold" : function(a) {
			return !$.rightoffold(a, {
				threshold : 0,
				container : window
			});
		}
	});

})(jQuery, window);
